Chapter 4 Hormonal Communication

Question 1

What are the 2 types of hormone?

Answer 1

• peptide hormones
• steroid hormones

Question 2

What are peptide hormones?

Answer 2

They are not soluble in the phospholipid membrane so do not enter the cell and need to bind to the cell surface membrane and release a second messenger inside the cell.

Question 3

What are steroid hormones?

Answer 3

They can pass through the membrane so enter the cell and the nucleus to have a direct effect on the DNA in the nucleus.

Question 4

What are some examples of peptide hormones?

Answer 4

• Adrenaline
• Insulin
• Glucagon

Question 5

What are some examples of steroid hormones?

Answer 5

• Oestrogen
• Testosterone

Question 6

What are endocrine glands?

Answer 6

Secrete hormones directly into the bloodstream

Question 7

What are exocrine glands?

Answer 7

Secrete hormones into a duct which carries the hormone to a specific part of the body, e.g. salivary gland

Question 8

What is the process following adrenaline reaching its target cell?

Answer 8

1.Adrenaline (1st messenger) binds to membrane receptor
2. This creates a conformational change causing the G-protein to split from the receptor
3. The G-protein becomes activated and combines with enzyme adenyl cyclase
4. Adenyl cyclase converts ATP into cyclic AMP (2nd messenger)
5. cAMP binds to and activates protein kinase
6. Protein kinase activates glycogen phosphorylase kinase which binds to glycogen phosphorylase
7. Glycogen phosphorylase catalyses the breakdown of glycogen into glucose

Question 9

Which hormones are secreted by the adrenal medulla?

Answer 9

Adrenaline and noradrenaline

Question 10

What are the 3 layers of the adrenal cortex?

Answer 10

• Zona glomerulosa
• Zona fasciculata
• Zona reticularis

Question 11

What is the Zona glomerulosa?

Answer 11

The outermost layer of adrenal cortex which secretes mineralocorticoids such as aldosterone, which contributes to maintaining blood pressure

Question 12

What is the Zona Fasciculata?

Answer 12

The middle layer of adrenal cortex which secretes glucocorticoids such as cortisol, which controls metabolism of carbohydrates, fats and proteins in the liver

Question 13

What is the Zona Reticularis?

Answer 13

The innermost layer of adrenal cortex, which is thought to secrete precursor molecules that are used to make sex hormones.

Question 14

What is the process of the action of steroid hormones?

Answer 14

1. The hormone passes through the phospholipid membrane of target cell
2. It then binds with a specific receptor (with a complementary shape) in the cytoplasm
3. The receptor-steroid hormone complex enters the nucleus of the target cell and binds to another specific receptor on the chromosomal material
4. Binding stimulates the production of mRNA molecules, which code for the production of proteins

Question 15

What are some roles of adrenaline in the body?

Answer 15

• relaxing smooth muscle in the bronchioles
• increasing stroke volume of the heart
• increasing heart rate
• dilating pupils
• causing body hair to stand erect
• stimulating conversion of glycogen to glucose

Question 16

What is the exocrine function of the pancreas?

Answer 16

Exocrine tissues synthesise and secrete pancreatic juices consisting of digestive enzymes into a duct which carries them to the small intestine.

Question 17

What is the endocrine function of the pancreas?

Answer 17

In the Islets of Langerhans alpha cells secrete glucagon and beta cells secrete insulin

Question 18

What is the structure of exocrine tissues in the pancreas?

Answer 18

Exocrine cells are in small groups called acini (singular acinus). Acini are grouped together into small lobules separated by connective tissue. The cells of the acini secrete enzymes into the tubule at the centre of the group. These tubules join to form intralobular ducts that combine to make the pancreatic duct.

Question 19

Where does the pancreatic duct carry fluid containing enzymes to?

Answer 19

first part of the small intestine - duodenum

Question 20

What fluid does the pancreatic duct contain?

Answer 20

Pancreatic amylase - digests amylose to maltose
Trypsinogen - an inactive protease which will be converted to the active form trypsin when it enters the duodenum
Lipase - digests lipid molecules

Question 21

What are the Islets of Langerhans?

Answer 21

Group of cells surrounded by acini and contain alpha and beta cells.

Question 22

What is the process of insulin being released from beta cells in the islets of Langerhans?

Answer 22

1. Potassium channels in the plasma membrane are normally open so potassium ions diffuse out of the cell making the inside more negative (-70mV)
2. When glucose concentrations are high, glucose enters the cell
3. Glucose is phosphorylated, then metabolised to produce ATP, using enzyme glucokinase
4. Presence of extra ATP causes potassium channels to close
5. Potassium ions cannot diffuse out of the cell, increasing the potential difference to -30mV as the inside becomes less negative
6. This change in potential difference opens calcium ion channels
7. Calcium ions enter the cell and cause vesicles containing insulin to fuse with the plasma membrane, releasing insulin by exocytosis

Question 23

What is hypoglycaemia?

Answer 23

When a person’s blood glucose concentration drops below 4mmol dm^-3

Question 24

What is hyperglycaemia?

Answer 24

When a person’s blood glucose concentration rises above 6mmol dm^-3

Question 25

What is the effect of hyperglycaemia on the pancreas, liver and muscles?

Answer 25

Beta cells in the pancreas secrete insulin into the blood and glucagon is inhibited. Glucose in the blood moves into the liver and muscles, which convert glucose into glycogen. This lowers the glucose level.

Question 26

What is the effect of hypoglycaemia on the pancreas, liver and muscles?

Answer 26

Alpha cells in the pancreas secrete glucagon and insulin is inhibited. Liver converts glycogen to glucose and glucose is released from the liver. This increased glucose levels.

Question 27

Define gluconeogenesis

Answer 27

The production of glucose from non-carbohydrate sources such as amino acids and lipids.

Question 28

Define glycogenolysis

Answer 28

The breakdown of glycogen into glucose by phosphorylase A.

Question 29

Define glycogenesis

Answer 29

The conversion of glucose into glycogen for storage.

Question 30

What is the process following insulin reaching its target cells?

Answer 30

1. Insulin binds to the membrane receptor 2. This activates enzyme tyrosine kinase which is associated with the receptor on the inside of the membrane 3. Tyrosine kinase causes phosphorylation of inactive enzymes to active enzymes in the cell 4. Vesicles containing glucose transporter proteins fuse with the membrane so more glucose can enter the cell 5. Some glucose in the cell is converted to glycogen for storage, some is converted to fats and some is used in respiration

Question 31

What is the process following glucagon reaching its target cells?

Answer 31

1. Glucagen binds to the membrane receptor 2. G-protein is stimulated and activated adenyl cyclase 3. Adenyl cyclase converts ATP to cAMP which activates a series of enzyme controlled reactions 4. Glycogen converts to glucose by phosphorylase A, amino acids and fats are converted to glucose and more fatty acids are used in respiration

Question 32

What is diabetes mellitus?

Answer 32

A condition in which blood glucose concentrations cannot be controlled effectively.

Question 33

What is type 1 diabetes?

Answer 33

Also known as insulin-dependent diabetes and is caused by an autoimmune response in which the immune system attacks and destroys beta cells so insulin cannot be produced.

Question 34

What is type 2 diabetes?

Answer 34

Also known as non-insulin-dependent diabetes and insulin receptors (in liver and fat storage tissues) become less responsive so cells cannot respond to insulin that is produced.

Question 35

What factors can cause type 2 diabetes?

Answer 35

- obesity - lack of regular exercise - diet high in sugars - family history - being of Asian/ Afro-Caribbean origin - increasing age

Question 36

How is Type 1 diabetes treated?

Answer 36

Insulin injections

Question 37

How is Type 2 diabetes treated?

Answer 37

- losing weight - more exercise - monitoring diet - insulin injections in severe cases

Question 38

What are advantages of using insulin from genetically modified bacteria?

Answer 38

- exact copy of human insulin so is faster acting and more effective - less chance of rejection due to immune response - lower risk of infection - cheaper to manufacture insulin than extract it from animals - the manufacturing process is more adaptable to demand - less chance of developing a tolerance to the insulin

Question 39

What are some alternatives to insulin injection?

Answer 39

- insulin pump therapy (small device that constantly pumps insulin through a needle that is permanently inserted under the skin - islet cell transplantation (transplant of healthy beta cells from the pancreas of a deceased donor) - a complete pancreas transplant

Question 40

How can lack of exercise cause diabetes?

Answer 40

Lack of exercise can cause muscle cells to lose sensitivity to insulin.